An automatic program to decompose a page description language input either into a raster version which can be printed directly by a target printer or into a raster version which can be exported in a portable and more editable form to another printer.
In a typical printer, the print controller will accept input files in any of several page description languages (PDLs) and color spaces, decompose the submissions, and then raster image process (RIP) them into a raster image specifically rendered for output on that printer. For CMYK printers, these output raster images are in the printer""s CMYK color space.
A problem arises when the same page must be printed, perhaps at a later date, on a different printer. Typically, for best image quality, the user must return to each page""s original source elements and repeat the decomposition, rendering, and rasterizing for the new printer. Not only does this represent a significant amount of additional overhead but, since the original submission files may no longer be available, this procedure may not be possible.
As an alternative, a stored copy of the final rasterized page image fully rendered for one printer could be used at the second device. Unfortunately, doing so would involve a loss of image quality. First, conversion from one printer""s color space to another""s color space is an inherently lossy process. Second, in generating the initial raster image, any available rendering hints would have been applied and hence would no longer be available. Once such fully rendered, printable rasters have been generated, the images are targeted for output on a specific machine, thereby reducing portability to other printers and their subsequent editability.
Hence, where different printers are available, it would be useful if a decomposer could automatically produce both (1) a raster version suitable for printing on the local printer and (2) a portable raster version preserving available rendering hints for storage which later could be exported to another printer. Doing so would allow the second machine to print a high quality image with less image quality degradation and reduced time consuming processing. Also, because any rendering hint information has been preserved, the impact on the output images of subsequent edits will be reduced.
In a color printing system, the print controller will generate a raster image for immediate printing and/or a portable and more editable raster image for export to another printer. If the request is for immediate printing, the raster image will be in the printer""s own color space (such as CMYK). If the request is for exporting the result, then the output raster typically will be in either the same CMYK color space as the input or in the portable device independent CIELAB color space. The output color space of exportable rasters can be determined either automatically from the input color space(s) or by user selection. PDL inputs in the CMYK color space will result in CMYK raster output, while PDL inputs in three valued color spaces (such as RGB or Lab) will be converted to CIELAB. On either alternative, any rendering hints will be preserved, thereby increasing image editability. Also, when creating CMYK export raster images, different versions of the CMYK color space (e.g., different printer specific CMYKs, SWOP CMYK, etc.) will be preserved rather than being converted to the target printer""s single version of CMYK. By selecting the color spaces of exportable raster images in this way, image quality will be improved.